Geology Reference
In-Depth Information
7 The Linyphiid spider fauna
(Araneae: Linyphiidae) of mountain
fores ts in the Easten Arc mo11ntains
NIKOLAJ SCHARFF
Africa with the number of species on mountains
in the northen hemisphere. This chapter des-
cribes the linyphiid fauna of the Eastern Arc
mountain forests (Figures 7.1 and 7.2). Informa-
ion comes from my own research (Scharff, 1989,
1990a, b, c, 1992) and data published elsewhere.
Forest faunas are difficult to define ecologi-
cally, since it is difficult to make a clear ecological
disincion between orest and non-forest species,
as species of more open habitats and species with
broad habitat preferences (ransgressor species)
intermingle with rue forest species. An example
of such a transgressor species is
Metalepyphantes
prei, us
(Simon
&
Fage, 1922), which is widely
distributed in the semi-arid African bushlands but
also extends its range into the African humid rain
forests. In this chapter, 'forest species' are
defined as any species recorded from forests and
'rue forest species' as species which have been
recorded only from forests, forest edges or gallery
forests (
Inroducion
The spider fauna of East Africa is not paricularly
well known, but one group of spiders, the sheet-
web weavers or dwarf spiders (family
Linyphiidae), is much better known than any
other group. This is quite strange since these
spiders are small (most spiders are less than 3 mm
in total lengh) and do not have any remarkable
body colours. The family Linyphiidae is one of
the largest spider families (second only to the
jumping spiders, Salicidae) with some 3600 spe-
cies described in 403 genera (Planick, 1989).
The common English names for these spiders
(dwarf or sheet-web spiders) are not very
appropriate, since linyphiids are not smaller than
spiders in several other families and sheet webs
resembling those of linyphiids are also built by
members of other spider families such as the
Theridiidae, Cyatholipidae, Digueidae, Pholci-
dae, Araneidae and Uloboridae (Eberhard, 1990).
Furthermore, sheet webs are built only by some
linyphiids, paricularly representaives of the sub-
family Linyphiinae.
An impressive amount of inormaion on the
East African linyphiid fauna has been published
during the last 30 years, especially on the mon-
tane fauna. In East Africa, many mountains have
now been explored at least once and this has
revealed a relaively rich linyphiid fauna.
However, 'rich' should be understood in an Afri-
can context, as the diversity is low if one compares
the number of species on each mountain in East
riverine forest), and therefore are
thought to be dependent on the forest habitat for
survival (see also Scharff, 1992).
=
he Linyphiid auna of the Easten Arc
montane orests
From a zoogeographical point of view, areas
should be deined by their monophyleic taxa and
such a situaion does not eist for linyphiids
within the geographical boundaries defined in this
topic. If the boundaries are extended to include
the Nyika Plateau and Viphya Mountains, in
115
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